Interpretive Summary: The sweetpotato weevil causes severe damage to roots and other parts of the sweetpotato plant, resulting in major losses of revenue and food calories each year around the world. In the USA, quarantine measures are in force in most southern States where the weevil is a problem. However, this has not stopped the spread of the weevil. In a USDA-funded project, we are studying the factors that contribute to the spread of the sweetpotato weevil to non-infested areas. We are also investigating the genetic variation of weevil populations in the USA and the Caribbean. Preliminary results show that there are significant genetic differences among weevil populations. Risk analysis studies showed that the overall risk of weevil introduction was low but nonetheless important risk level in a country where a single weevil could lead to the rejection of an entire crop and the imposition of strict quarantine measures with severe economic impact to growers.

Technical Abstract:
The sweetpotato weevil, Cylas formicarius, causes severe damage to roots and other parts of the sweetpotato plant, resulting in major losses of revenue and food calories each year around the world. In the USA, quarantine measures are in force in most southern States where the weevil is a problem. However, this has not stopped the spread of the weevil. In a USDA-funded project, we are studying the factors that contribute to the spread of the sweetpotato weevil to non-infested areas. We are also investigating the genetic variation of C. formicarius populations in the USA and the Caribbean. Preliminary results show that sufficient polymorphism exists among weevil populations to suggest important differences in these populations. Risk analysis studies showed that the probability of weevil introduction into a new area without any mitigation measures was 0.2667. The probability of weevil introduction following a pre-harvest mitigation effort was 0.1175, and the probability of introduction following post-harvest mitigation was 0.000517. The calculated overall risk of weevil introduction was 0.0000162, a low but nonetheless important risk level in a country where a single weevil could lead to the rejection of an entire crop and the imposition of strict quarantine measures with severe economic impact to growers. There are locations where no weevil infestations have ever been reported; GIS-aided studies will determine the environmental conditions that foster weevil establishment and thus provide a means of identifying “high risk” areas for weevil spread. We propose the formation of a network to conduct similar studies in other parts of the world.